The invention relates in general to noninvasive methods and instruments for measuring blood pressure, and in particular, to an automatic sphygmomanometer worn by a patient for monitoring blood pressure during prolonged periods while conducting normal daily activities.
Blood pressure is subject to continuous variations tied to several factors including age, sex, environment, season, temperature, altitude and the like. Moreover, blood pressure of a subject may vary during the day because of many contingent factors including posture, respiration, and the state of muscular and/or cerebral activity. In particular, physical exertion may cause large increases in blood pressure.
Significant variations of blood pressure due to other factors than those noted above may indicate that the circulatory system and/or the heart is malfunctioning. For these reasons, it is useful to check the blood pressure throughout the entire day to study the magnitude of the variations and the presence of possible anomalies.
For these reasons, so-called pressure Holters are widely used. These portable instruments are automatic sphygmomanometers that are easy to use and are of minimum size which, when worn by the patient, measures the blood pressure at preset intervals of time. A limitation of these portable instruments is primarily tied to the difficulty of associating the measured value of blood pressure to the current conditions of the patient at the time of the measurement.
Not knowing the actual conditions at the time of measurement, the recorded reading may be wrongly interpreted and it is very difficult to find out and recognize the magnitude of these errors. It is evident that there is a need and/or utility for a blood pressure Holter capable of assessing the conditions that may influence the measured values of blood pressure, and in particular, the state of physical exertion of the patient because of the strong influence that it has on arterial pressure.
An object of the invention is to provide an intelligent instrument that is more reliable in terms of the data it provides, and moreover, is capable of automatically managing the measurement operations.
According to the present invention, a blood pressure Holter system includes a system of classification of the current state of physical exertion as detected by one or more movement sensors, and is based on a fuzzy logic possessing according to predefined algorithms.
According to another important aspect of the blood pressure Holter system, the inflating/deflating of the constricting pneumatic sleeve as well as the processing of the signals generated by the pressure sensor for calculating the maximum and minimum arterial pressures are coordinated by the on-board fuzzy logic microcontroller. In this way, the inflating of the sleeve is less traumatic for the patient while the determination of the maximum and minimum values of the blood pressure is carried out in a substantially identical manner as a doctor would do manually. This is by virtue of the intrinsic peculiarity of controlling the inflating/deflating of the sleeve, and of processing the pressure signal carried out according to a fuzzy logic algorithm.
Besides correlating the blood pressure measurements with corresponding evaluation data on the state of exertion of the patient at the moment of the measurement, the instrument may optionally self-program itself by exploiting the information on the current physical activity even to time the carrying out of new pressure measurements.
For example, to avoid spurious measurements if the patient is doing a particularly intense physical activity, a scheduled measurement may be automatically postponed by the Holter system. In contrast, by checking the results of most recent blood pressure readings, if anomalies are detected, the Holter system may automatically decide to increase the frequency of measurements.